Robot cleaner and control method for the same

ABSTRACT

A robot cleaner includes a body to travel on a floor, an obstacle sensing unit to sense an obstacle approaching the body, an auxiliary cleaning unit mounted to a bottom of the body, to be extendable and retractable, and a control unit to control extension or retraction of the auxiliary cleaning unit when the obstacle is sensed, through adjustment of an extension or retraction degree of the auxiliary cleaning unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application Nos.10-2011-106678 and 10-2012-22469, respectively filed on Oct. 18, 2011and Mar. 5, 2012 in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a robot cleaner and acontrol method for the same, which are capable of automatically cleaninga region to be cleaned by removing dust or the like from a floor of thecleaning region while traveling about the cleaning region.

2. Description of the Related Art

A robot cleaner is a device for automatically cleaning a region to becleaned by sucking foreign matter such as dust from a floor of thecleaning region while autonomously traveling about the cleaning regionwithout being operated by a user. Such a robot cleaner not only includesa main brush to remove dust or the like accumulated on a region beneatha body of the robot cleaner, but also includes an auxiliary cleaningtool to achieve an enhancement in cleaning performance in a regionadjacent to a wall.

Such an auxiliary cleaning tool is outwardly protruded from an inside ofthe robot cleaner body, to sweep dust on a floor, in particular, dust ina region adjacent to a wall. Although such an auxiliary cleaning toolachieves an enhancement in cleaning performance in a region adjacent toa wall, there may be a problem in that the auxiliary cleaning tool hasan increased possibility of striking the wall because it is outwardlyprotruded from the robot cleaner body. In a conventional robot cleaner,however, it may be impossible to prevent the auxiliary cleaning toolfrom striking an obstacle because protrusion of the auxiliary cleaningtool is not accurately controlled. For this reason, the auxiliarycleaning tool may interfere with travel of the robot cleaner.Consequently, it may be impossible to achieve efficient cleaning in aregion adjacent to a wall.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a robotcleaner and a control method for the same, which are capable ofadjusting an extension or retraction degree of an auxiliary cleaningunit when an obstacle is sensed.

Another aspect of the present disclosure is to provide a robot cleanerand a control method for the same, which are capable of controllingextension or retraction of an auxiliary cleaning unit in accordance withthe shape of an obstacle.

Another aspect of the present disclosure is to provide a robot cleanerand a control method for the same, which are capable of controllingextension or retraction of an auxiliary cleaning unit in accordance witha travel direction of a body of the robot cleaner.

Another aspect of the present disclosure is to provide a robot cleanerand a control method for the same, which are capable of controllingextension or retraction of an auxiliary cleaning unit in accordance witha cleaning mode.

Additional aspects of the disclosure will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

In accordance with one aspect of the present disclosure, a robot cleanerincludes a body to travel on a floor, an obstacle sensing unit to sensean obstacle approaching the body, an auxiliary cleaning unit mounted toa bottom of the body, to be extendable and retractable, and a controlunit to control extension or retraction of the auxiliary cleaning unitwhen the obstacle is sensed, through adjustment of an extension orretraction degree of the auxiliary cleaning unit.

The auxiliary cleaning unit may be pivotably mounted to the bottom ofthe body. The control unit may adjust the extension or retraction of theauxiliary cleaning unit, based on a pivot angle formed by the auxiliarycleaning unit with respect to a travel direction of the body.

The control unit may adjust the extension or retraction degree of theauxiliary cleaning unit such that a distance between an outermostportion of the auxiliary cleaning unit and the obstacle is greater thana predetermined first critical value, but smaller than a predeterminedsecond critical value.

The control unit may compare an output signal from the obstacle sensingunit according to a sensing direction of the obstacle sensing unit witha predetermined critical value, and adjusts the extension or retractiondegree of the auxiliary cleaning unit, based on a result of thecomparison.

The predetermined critical value may correspond to a distance from thebody to an outermost portion of the auxiliary cleaning unit.

The control unit may adjust the extension or retraction degree of theauxiliary cleaning unit, based on an output signal from the obstaclesensing unit according to an extension direction of the auxiliarycleaning unit.

The control unit may adjust the extension or retraction degree of theauxiliary cleaning unit in proportion to the output signal.

In accordance with another aspect of the present disclosure, a robotcleaner includes a body to travel on a floor, an obstacle sensing unitto sense an obstacle approaching the body, at least one auxiliarycleaning unit mounted to a bottom of the body, to be extendable andretractable, and a control unit to control extension or retraction ofthe auxiliary cleaning unit when the obstacle is sensed, in accordancewith a shape of the sensed obstacle.

The control unit may control the extension or retraction of theauxiliary cleaning unit when the obstacle has a flat wall shape suchthat the auxiliary cleaning unit is retracted after being maintained inan extended state for a predetermined time, or is extended after beingmaintained in a retracted state for a predetermined time.

The at least one auxiliary cleaning unit may include at least twoauxiliary cleaning units mounted to the bottom of the body. When theobstacle is sensed only at a lateral side of the body, the control unitmay only control extension or retraction of the auxiliary cleaning unit,which is disposed in a direction corresponding to the obstacle, amongthe at least two auxiliary cleaning units.

The at least one auxiliary cleaning unit may include at least twoauxiliary cleaning units mounted to the bottom of the body. When theobstacle has a corner wall shape, the control unit may control extensionor retraction of the auxiliary cleaning units, which are disposed atopposite sides of the body, among the at least two auxiliary cleaningunits.

The control unit may control the extension or retraction of theauxiliary cleaning unit when the shape of the obstacle has a smallersize than a reference size.

In accordance with another aspect of the present disclosure, a robotcleaner includes a body to travel on a floor, an obstacle sensing unitto sense an obstacle approaching the body, at least one auxiliarycleaning unit mounted to a bottom of the body, to be extendable andretractable, and a control unit to control extension or retraction ofthe auxiliary cleaning unit when the obstacle is sensed, in accordancewith a travel direction of the body.

The control unit may control the auxiliary cleaning unit to be retractedbefore and after rotation of the body or before and after backwardmovement of the body.

The at least one auxiliary cleaning unit may include at least twoauxiliary cleaning units mounted to the bottom of the body around thebody. The control unit may control extension or retraction of theauxiliary cleaning units in accordance with a rotation direction of thebody such that a preceding one of the auxiliary cleaning units in therotation direction of the body is retracted.

The control unit may control extension degrees of the auxiliary cleaningunits in accordance with a rotation direction of the body such that apreceding one of the auxiliary cleaning units in a direction opposite tothe rotation direction of the body has an increased extension degree.

The control unit may adjust a travel speed of the body or a rotationspeed of an auxiliary cleaning tool coupled to the auxiliary cleaningunit when the body rotates.

In accordance with another aspect of the present disclosure, a robotcleaner includes a body to travel on a floor, an obstacle sensing unitto sense an obstacle approaching the body, an auxiliary cleaning unitmounted to a bottom of the body, to be extendable and retractable, and acontrol unit to control extension or retraction of the auxiliarycleaning unit when the obstacle is sensed, in accordance with a cleaningmode of the body.

The control unit may perform a control operation to prevent theauxiliary cleaning unit from extending when a cleaning operation iscompleted.

The control unit may perform a control operation to prevent theauxiliary cleaning unit from extending when the obstacle is determinedto be a charger or an exhaust station during return of the body to thecharger or the exhaust station.

The robot cleaner may further include a signal sensing unit to sense adiscriminating signal for the charger or the exhaust station.

The discriminating signal may be an infrared signal, a radio frequency(RF) signal, or a magnetic field signal.

The control unit may perform a control operation to prevent theauxiliary cleaning unit from extending for a predetermined time when acleaning operation starts in accordance with an automatic cleaning mode.

The control unit may perform a control operation to prevent theauxiliary cleaning unit from extending when the body performs a chargingoperation.

The control unit may perform a control operation to prevent theauxiliary cleaning unit from extending when the charging operation ofthe body is completed or when supply of electric power to the charger isstopped.

In accordance with still another aspect of the present disclosure, acontrol method for a robot cleaner includes driving a body of the robotcleaner such that the body travels on a floor, sensing an obstacleapproaching the body, and controlling extension or retraction of anauxiliary cleaning unit mounted to a bottom of the body, to beextendable and retractable, through adjustment of an extension orretraction degree of the auxiliary cleaning unit.

The auxiliary cleaning unit may be pivotably mounted to the bottom ofthe body. The controlling the extension or retraction of the auxiliarycleaning unit may be executed based on a pivot angle formed by theauxiliary cleaning unit with respect to a travel direction of the body.

The controlling the extension or retraction of the auxiliary cleaningunit may be executed such that a distance between an outermost portionof the auxiliary cleaning unit and the obstacle is greater than apredetermined first critical value, but smaller than a predeterminedsecond critical value.

The controlling the extension or retraction of the auxiliary cleaningunit may be executed based on a result of a comparison between an outputsignal from the obstacle sensing unit according to a sensing directionof the obstacle sensing unit and a predetermined critical value.

The predetermined critical value may correspond to a distance from thebody to an outermost portion of the auxiliary cleaning unit.

The controlling the extension or retraction of the auxiliary cleaningunit may be executed, based on an output signal according to an obstaclesensing direction, along which the auxiliary cleaning unit extends.

The controlling the extension or retraction of the auxiliary cleaningunit may be executed in proportion to the output signal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent andmore readily appreciated from the following description of theembodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a view schematically illustrating an outer appearance of arobot cleaner according to an exemplary embodiment of the presentdisclosure;

FIG. 2 is a bottom view schematically illustrating a configuration ofthe robot cleaner shown in FIG. 1;

FIG. 3 is a view schematically illustrating a configuration forextending or retracting auxiliary cleaning units in accordance with anembodiment of the present disclosure;

FIG. 4 is a view schematically illustrating a configuration forextending or retracting the auxiliary cleaning units in accordance withanother embodiment of the present disclosure;

FIG. 5 is a view schematically illustrating a configuration of anauxiliary cleaning tool according to an exemplary embodiment of thepresent disclosure;

FIG. 6 is a view schematically illustrating a configuration of theauxiliary cleaning tool according to another embodiment of the presentdisclosure;

FIG. 7 is a block diagram schematically illustrating a controlconfiguration of the robot cleaner according to an exemplary embodimentof the present disclosure;

FIG. 8 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with an embodiment of thepresent disclosure;

FIG. 9 is a view schematically illustrating operation of the robotcleaner according to the embodiment of FIG. 8;

FIG. 10 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with another embodiment ofthe present disclosure;

FIG. 11 is a view schematically illustrating operation of the robotcleaner according to the embodiment of FIG. 10;

FIG. 12 is a graph schematically depicting obstacle sensing results ofthe robot cleaner according to the embodiment of FIG. 10;

FIG. 13 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with another embodiment ofthe present disclosure;

FIG. 14 is a view schematically illustrating operation of the robotcleaner according to the embodiment of FIG. 13;

FIG. 15 is a graph schematically depicting obstacle sensing results ofthe robot cleaner according to the embodiment of FIG. 13;

FIGS. 16 to 18 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure;

FIGS. 19 to 21 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure;and

FIGS. 22 to 24 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings.

FIG. 1 is a view schematically illustrating an outer appearance of arobot cleaner according to an exemplary embodiment of the presentdisclosure.

Referring to FIG. 1, the robot cleaner, which is designated by referencenumeral “1”, includes a body 10 to define an outer appearance of therobot cleaner 1.

Various sensors are mounted to the body 10, to sense an obstacle. Thesensors may include a proximity sensor 61 and/or a vision sensor 62. Forexample, when the robot cleaner 1 travels in a random direction underthe condition that there is no predetermined path along which the robotcleaner 1 travels, that is, in a cleaning system having no map, therobot cleaner 1 may travel about a cleaning region and sense anobstacle, using the proximity sensor 61. On the other hand, when therobot cleaner 1 travels along a predetermined path, that is, in acleaning system requiring a map, the vision sensor 62 may be installedto receive position information of the robot cleaner 1, and thus tocreate a map. The sensors may be implemented in various manners.

A signal sensor 63 may also be mounted to the body 10, to receive asignal from a charger or an exhaust station.

A display unit 64 is coupled to the body 10, to display various statesof the robot cleaner 1. For example, the display unit 64 may display acharged state of the battery, whether or not the dust collector 55 isfull of dust, a cleaning mode of the robot cleaner 1, etc.

Configurations of the auxiliary cleaning units 21 and 22 will bedescribed in more detail with reference to FIGS. 2 to 6.

FIG. 2 is a bottom view schematically illustrating a configuration ofthe robot cleaner shown in FIG. 1.

Referring to FIG. 2, the robot cleaner 1 includes a main brush unit 30,a power supply 50, drive wheels 41 and 42, a caster 43, and theauxiliary cleaning units 21 and 22.

The main brush unit 30 is mounted at an opening formed at a portion ofthe bottom of the body 10 biased from a central region of the body 10 ina rearward direction R. The main brush unit 30 sweeps dust accumulatedon the floor, on which the body 10 is disposed, such that the swept dustis guided to a dust inlet 33. The opening of the bottom of the body 10,at which the main brush unit 30 is mounted, functions as the dust inlet33.

The main brush unit 30 includes a roller 31, and a main brush 32attached to an outer surface of the roller 31. As the roller 31 rotates,the main brush 32 sweeps dust accumulated on the floor such that theswept dust is guided to the dust inlet 33.

Although not shown in FIG. 2, a fan unit to generate suction force isprovided within the dust inlet 33. The fan unit functions to move dustintroduced into the dust inlet 33 to a dust collector.

The power supply 50 supplies drive power to drive the body 10. The powersupply 50 includes a battery electrically connected to the body 10 anddrivers to drive various elements mounted to the body 10, to supplydrive power to the body 10 and drivers. The battery is constituted by arechargeable secondary battery. When the body 10 is coupled to a chargeror an exhaust station after completing a cleaning operation, the batteryreceives electric power from the charger or exhaust station, to becharged.

The drive wheels 41 and 42 are centrally arranged at opposite sides ofthe bottom of the body 10 in a symmetrical manner, respectively. Thedrive wheels 41 and 42 may perform movement operations including forwardmovement, backward movement, and rotation during cleaning.

The caster 43 is installed at a front edge portion of the bottom of thebody 10 when viewed on the basis of a travel direction. The caster 43enables the body 10 to keep a stable posture. The drive wheels 41 and42, and caster 43 may be configured into a single assembly detachablymounted to the body 10.

Openings are formed at opposite sides of a front portion of the body 10when viewed on the basis of a forward direction F, respectively. Theauxiliary cleaning units 21 and 22 are installed to cover the openings,respectively.

FIG. 3 is a view schematically illustrating a configuration forextending or retracting the auxiliary cleaning units in accordance withan embodiment of the present disclosure.

Referring to FIG. 3, each of the auxiliary cleaning units 21 and 22includes a side arm 102, a periphery cover 103, and an auxiliarycleaning tool 110 (see FIGS. 5 and 6).

The side arm 102 is coupled to a front portion of the bottom of the body10 at one side of the body 10. An arm motor (not shown) is received inthe body 10 over the side arm 102, to drive the side arm 102. The armmotor is connected to a rotation shaft (not shown) via gears to transmitdrive force to the side arm 102. The rotation shaft is mounted to acoupling groove 101 formed at one end of the side arm 102.

When the arm motor drives, the rotation shaft is rotated, therebycausing the side arm 102 to pivot about the coupling groove 101. In thiscase, the side arm 102 pivots outwardly of the body 10. In this state,the periphery cover 103 no longer covers the opening of the body 10.That is, the periphery cover 103 no longer forms the periphery of thebody 10.

A coupling groove 104, to which the auxiliary cleaning tool 110 iscoupled, is formed at the other end of the side arm 102. A rotationmotor (not shown) is received in the body 10 over the coupling groove104, to drive the auxiliary cleaning tool 110. The auxiliary cleaningtool 110 is rotated about the coupling groove 104 by drive force of therotation motor.

FIG. 4 is a view schematically illustrating a configuration forextending or retracting the auxiliary cleaning units in accordance withanother embodiment of the present disclosure.

Referring to FIG. 4, each of the auxiliary cleaning units 21 and 22includes a side arm 106, a periphery cover 108, and an auxiliarycleaning tool 110 (see FIGS. 5 and 6).

The side arm 106 is coupled to a front portion of the bottom of the body10 at one side of the body 10 via a coupling groove 105. An extensionarm 107 is received in the side arm 106 such that it is extendableoutwardly of the side arm 106 in a sliding manner.

The extension arm 107 moves forward and rearward within the side arm 106in a longitudinal direction of the side arm 106. To this end, a rail isformed within the side arm 106, and a guide (not shown), which isengaged with the rail, is formed at the extension arm 107. Accordingly,the extension arm 107 may slidably move along the rail in a state ofbeing coupled to the rail. Another extension arm may be received in theextension arm 107 such that it is extendable outwardly of the extensionarm 107 in a sliding manner. Meanwhile, movement of the anotherextension arm may be carried out in the same manner as described above.There is no limitation as to the number of extension arms.

An arm motor (not shown) is received in the body 10 over the side arm106, to drive the extension arm 107. The arm motor transmits drive forceto the extension arm 107 via gears. When the arm motor drives, theextension arm 107 slides outwardly of the side arm 106, to extendoutwardly of the body 10. In this state, the periphery cover 108 nolonger covers the opening of the body 10. That is, the periphery cover108 no longer forms the periphery of the body 10.

A coupling groove 109, to which the auxiliary cleaning tool 110 iscoupled, is formed at one end of the extension arm 107. A rotation motor(not shown) is received in the body over the coupling groove 109, todrive the auxiliary cleaning tool 110. The auxiliary cleaning tool 110is rotated about the coupling groove 109 by drive force of the rotationmotor.

FIG. 5 is a view schematically illustrating a configuration of theauxiliary cleaning tool according to an exemplary embodiment of thepresent disclosure.

Referring to FIG. 5, the auxiliary cleaning tool 110 includes brush arms113 coupled to form a central common end such that they outwardly extendin a radial direction from the central common end while being spacedapart from one another in a circumferential direction. An auxiliarybrush 112 is coupled to each brush arm 113. A rotation shaft 114 isformed at the central common end of the brush arms 113. The rotationshaft 114 extends to be coupled to the side arm 102 or extension arm 106via the coupling groove 104 or 109. When the auxiliary cleaning tool 110rotates, the auxiliary brush 112 sweeps dust accumulated on an areadisposed adjacent to a wall toward the central region of the body 10 ordisperses the dust.

FIG. 6 is a view schematically illustrating a configuration of theauxiliary cleaning tool according to another embodiment of the presentdisclosure.

Referring to FIG. 6, the auxiliary cleaning tool 110′ includes acircular floorcloth holder 116. An auxiliary floorcloth 115 is fittedaround the floorcloth holder 116 in a radial direction. A rotation shaft114 is formed at a center of the floorcloth holder 116 such that itaxially extends. The rotation shaft 114 receives drive force from arotation motor, to rotate the auxiliary cleaning tool 110′. The rotationshaft 114 is coupled to the side arm 102 or extension arm 106 via thecoupling groove 104 or 109. When the auxiliary cleaning tool 110′rotates, the auxiliary floorcloth 115 scrubs an area disposed adjacentto a wall.

Meanwhile, the auxiliary brush 112 may be made of various materialshaving elasticity. The auxiliary floorcloth 115 may be made of a fibermaterial or various materials other than the fiber material.

The robot cleaner 1 according to the illustrated embodiment of thepresent disclosure may clean even an area of the floor disposed adjacentto a wall or a corner area of the floor because the effective cleaningregion of the robot cleaner 1 is extended by virtue of the auxiliarycleaning units 21 and 22 outwardly extendable from the body 10.

In the following description, it is assumed that extension of eachauxiliary cleaning units 21 or 22 carried out during operation of theauxiliary cleaning units 21 or 22 include both pivotal movement of theside arm 102 outwardly of the body 10 in the embodiment of FIG. 3 andextension of the extension arm 106 outwardly of the body 10 in theembodiment of FIG. 4, except for the case in which the extension of eachauxiliary cleaning unit 21 or 22 is separately described in conjunctionwith pivotal movement of the side arm 102 or the extension of theextension arm 106. Also, it is assumed that the auxiliary cleaning tool110 cleans an area of the floor disposed adjacent to a wall or a cornerarea of the floor while rotating during cleaning operation of the robotcleaner 1.

FIG. 7 is a block diagram schematically illustrating a controlconfiguration of the robot cleaner according to an exemplary embodimentof the present disclosure.

Referring to FIG. 7, the robot cleaner 1 includes an input unit 210, anobstacle sensing unit 220, a signal sensing unit 230, a control unit240, a body driver 250, a main brush unit driver 260, and an auxiliarycleaning unit driver 270.

The input unit 210 receives a user's operation command from an operationpanel provided at the body 10 or a remote controller. The user'soperation command includes commands associated with travel, cleaning andcharging operations of the robot cleaner 1. In particular, the userdirectly operates the remote controller, to input a command associatedwith, for example, protrusion of the auxiliary cleaning units 21 and 22.

The obstacle sensing unit 220 senses an obstacle approaching the body 10during travel of the body 10. In more detail, the obstacle sensing unit220 receives information as to obstacles from the proximity sensor 61 orvision sensor 62, and then senses an obstacle disposed around the body10.

For example, the proximity sensor 61 may be implemented in the form ofan ultrasonic sensor. In this case, the proximity sensor 61 may transmitan ultrasonic wave, and then receive an ultrasonic wave reflected froman obstacle, thereby sensing the obstacle. For this function, theproximity sensor 61 may have the form of a combination of at least oneultrasonic transmitter and at least one ultrasonic receiver installedaround the periphery of the body 10. When the ultrasonic proximitysensor 61 further approaches an obstacle, it generates a signal havinghigher power because the intensity of an ultrasonic wave received by theultrasonic proximity sensor 61 after being reflected from the obstacleincreases. It may be possible to calculate the distance between the body10 and the obstacle, based on the output signal from the proximitysensor 61.

Meanwhile, the vision sensor 62 acquires an image on the travel path ofthe body 10, and then senses an obstacle through processing of theacquired image. Practically, it may be possible to calculate thedistance between the body 10 and the obstacle in the image processed bythe vision sensor 62, based on three-dimensional coordinates.

The signal sensing unit 230 senses a discriminating signal transmittedfrom the charger or formed around the charger in accordance withoperation of the signal sensor 63.

The body driver 250 drives the drive wheels 41 and 42, to move the robotcleaner 1. In accordance with a control command from a travel controller242, the body driver 250 controls the travel direction and travel speedof the robot cleaner 1.

The main brush unit driver 260 drives the roller 31 in accordance with acontrol command from a cleaning controller 241. In accordance withrotation of the roller 31, the main brush 32 sweeps dust accumulated onthe floor.

The auxiliary cleaning unit driver 270 drives the arm motor inaccordance with a control command from the cleaning controller 241, toperform extension or retraction of each auxiliary cleaning unit 21 or22. The auxiliary cleaning unit driver 270 also adjusts an extension orretraction degree of each auxiliary cleaning unit 21 or 22 by adjustingthe number of rotations of the arm motor in accordance with the distancebetween the body 10 and the obstacle. The auxiliary cleaning unit driver270 also performs rotation of the auxiliary cleaning tool 110 andadjusts the rotation speed of the auxiliary cleaning tool 110, to causethe auxiliary brush 112 (or the rotation speed of the auxiliary cleaningtool 110′, to cause auxiliary floorcloth 115) to clean an area disposedadjacent to a wall.

The control unit 240 controls the overall operation of the robot cleaner1 in accordance with a control program. The control unit 240 mainlyincludes the cleaning controller 241, which controls cleaning operationof the robot cleaner 1, the travel controller 242, which controls travelof the robot cleaner 1, and a charging controller 243 to control acharging operation of the robot cleaner 1.

The cleaning controller 241 not only controls operation of the mainbrush unit 30, but also determines whether each auxiliary cleaning unit21 or 22 is to be extended or retracted. The cleaning controller 241also controls an extension or retraction degree of each auxiliarycleaning unit 21 or 22. Also, the cleaning controller 241 determines anoperation mode of the robot cleaner 1 among an automatic cleaning mode,a charging mode, a charging completion mode, a charging stop mode, etc.,and controls extension or retraction of each auxiliary cleaning unit 21or 22 in accordance with the determined operation mode.

The travel controller 242 controls forward movement, backward movementand rotation of the body 10. In more detail, the travel controller 242controls rotation directions and speed of the drive wheels 41 and 42.When it is sensed that there is an obstacle on the travel path of thebody 10, the travel controller 242 also determines whether the body 10has to turn to the left or to the right or has to move backward.

The charging controller 243 controls the robot cleaner 1 to return tothe charger or to the exhaust station when cleaning operation iscompleted, to cause the robot cleaner 1 to be charged. When a chargingoperation is carried out in a state in which the body 10 docks with thecharger, the charging controller 243 determines a charged state of therobot cleaner 1. That is, the charging controller 243 may determine acompletely charged state, a power shut-off state of the charger duringcharging operation, etc.

Hereinafter, methods for controlling extension and retraction of theauxiliary cleaning units of the above-described robot cleaner inaccordance with embodiments of the present disclosure will be described.

FIG. 8 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with an embodiment of thepresent disclosure. FIG. 9 is a view schematically illustratingoperation of the robot cleaner according to the embodiment of FIG. 8.

Referring to FIGS. 8 and 9, the obstacle sensing unit 220 senses anobstacle approaching the body 10 (410). Thereafter, the cleaningcontroller 241 calculates the distance from the auxiliary cleaning unit21 to the obstacle, namely, a distance L (420). In detail, the cleaningcontroller 241 may calculate the distance L from the rotation shaft ofthe auxiliary cleaning unit 21 to the obstacle, based on an outputsignal from the proximity sensor 61.

Subsequently, the cleaning controller 241 calculates a distance D2, bywhich the auxiliary cleaning unit 21 is extendable (430). The extendabledistance D2 of the auxiliary cleaning unit 21 in a travel direction ofthe body 10 may be calculated, based on a rotation radius R of the sidearm 102 and a rotation radius rof the auxiliary cleaning tool 110. Here,the rotation radius rof the auxiliary cleaning tool 110 represents therotation radius of the brush arm 113 (or floorcloth holder 116 ofauxiliary cleaning tool 110′), which does not have elasticity. Indetail, the extendable distance D2 of the auxiliary cleaning unit 21 maybe calculated through the following Expression:

Expression

D2=R*COS θ+r

In the Expression, “θ” represents an angle formed by the side arm 102with respect to the travel direction of the body 10. The auxiliarycleaning unit 21 may extend by a distance determined based on the angleθ while crossing a rotation path 310 of the side arm 102 and a rotationpath 320 of the auxiliary cleaning tool 110.

Also, the extendable distance D2 of the auxiliary cleaning unit 21 toprevent the outermost portion of the auxiliary cleaning unit 21 fromstriking the obstacle is calculated. Here, the outermost portion of theauxiliary cleaning unit 21 represents an outermost peripheral portion ofthe rotating brush arm 113 (or floorcloth holder 116 of auxiliarycleaning tool 110′) in the travel direction of the body 10. Accordingly,the auxiliary brush 112, which is made of an elastic material (or theauxiliary floorcloth 115, which is made of a fiber material) may performcleaning in contact with an area disposed adjacent to a wall whilerotating along a rotation path 330.

Thereafter, the cleaning controller 241 adjusts the extension distanceof the auxiliary cleaning unit 21, and then controls the auxiliarycleaning unit 21 to extend by the adjusted extension distance (440). Inthis case, the extension distance of the auxiliary cleaning unit 231 isassociated with the pivot angle of the side arm 102. The pivot angle ofthe side arm 102 is associated with the angle θ.

The cleaning controller 241 adjusts the pivot angle of the side arm 102and, as such, the distance D1 between the outermost portion of theauxiliary cleaning unit 21 and the obstacle is adjusted. The distance D1may be calculated by a difference between the distance L from therotation shaft of the auxiliary cleaning unit 21 to the obstacle and theextension distance of the auxiliary cleaning unit 21, that is, thedistance D2. The pivot angle of the auxiliary cleaning unit 21 may beadjusted such that the distance D1 between the outermost portion of theauxiliary cleaning unit 21 and the obstacle is greater than apredetermined first critical value, but smaller than a predeterminedsecond critical value.

FIG. 10 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with another embodiment ofthe present disclosure. FIG. 11 is a view schematically illustratingoperation of the robot cleaner according to the embodiment of FIG. 10.For convenience of description, this method will be described inconjunction with the embodiment of FIG. 3.

Referring to FIGS. 10 and 11, the obstacle sensing unit 220 senses anobstacle approaching the body 10 (510). At least one proximity sensor 61is installed at the periphery of the body 10. The proximity sensor 61senses an obstacle in a sensing direction thereof. In the illustratedcase, a plurality of proximity sensors 61 is installed.

Thereafter, the cleaning controller 241 analyzes results of obstaclesensing in accordance with positions of the proximity sensors 61 (520).Through analysis of the obstacle sensing results, it may be seen thatoutput signals from the proximity sensors 61 exhibit differentintensities in accordance with different sensing directions of theproximity sensors 61, as shown in FIG. 12. For example, when an obstacleis disposed in the travel direction of the body 10, output signals fromthe proximity sensors 61 exhibit higher intensities in the arrangementorder of the proximity sensors 61 nearer to the front of the body 10. Inthe illustrated case, it may be possible to calculate the distance tothe obstacle, based on the output signal from the proximity sensor 61disposed at a sensor position A.

The cleaning controller 241 analyzes whether the output signal from eachproximity sensor 61 is higher or lower than a predetermined criticalvalue. Here, the critical value corresponds to the distance from thebody 10 to the outermost portion of the auxiliary cleaning unit 21 inthe travel direction of the body 10.

Subsequently, the cleaning controller 241 determines an extensionposition of the auxiliary cleaning unit 21, based on the results ofanalysis (530). The auxiliary cleaning unit 21 may extend to theextension position while crossing the rotation path 310 of the side arm102 and the rotation path 320 of the auxiliary cleaning tool 110. Theextension position of the auxiliary cleaning unit 21 corresponds to aposition on the rotation path 310 of the side arm 102

When the output signal from the proximity sensor 61 is higher than thepredetermined critical value, the cleaning controller 241 may determinethat, in association with the position of the proximity sensor 61, thereis an insufficient space to allow the auxiliary cleaning unit 21 toextend. In this case, from among the proximity sensors 61, each of whichoutputs a signal lower than the critical value, one proximity sensor 61outputting a signal having highest intensity is selected. Afterdetermining the position of the selected proximity sensor 61, thecleaning controller 241 determines an extension position of theauxiliary cleaning unit 21 on the rotation path 310 of the side arm 102,based on the determined position of the proximity sensor 61.

On the other hand, when the output signal from the proximity sensor 61is lower than the predetermined critical value, the cleaning controller241 may determine that, in association with the position of theproximity sensor 61, there is a sufficient space to allow the auxiliarycleaning unit 21 to extend. In this case, the cleaning controller 241determines the position of the proximity sensor 61, and then determinesan extension position of the auxiliary cleaning unit 21 on the rotationpath 310 of the side arm 102, based on the determined position of theproximity sensor 61.

Alternatively, it may be possible to determine an extension position ofthe auxiliary cleaning unit 21 on the rotation path 310 of the side arm102, based on an intermediate position between the position of theproximity sensor 61 outputting a highest-intensity signal and theposition of the proximity sensor 61 outputting a second higher-intensitysignal.

Thereafter, the cleaning controller 241 adjusts a pivot angle of theside arm 102, based on the determined extension position, to cause theauxiliary cleaning unit 21 to extend to the determined extensionposition (540).

FIG. 13 is a flowchart schematically illustrating a method forcontrolling the robot cleaner in accordance with another embodiment ofthe present disclosure. FIG. 14 is a view schematically illustratingoperation of the robot cleaner according to the embodiment of FIG. 13.For convenience of description, this method will be described inconjunction with the embodiment of FIG. 4.

Referring to FIGS. 13 and 14, the obstacle sensing unit 220 senses anobstacle approaching the body 10 (610).

Thereafter, the cleaning controller 241 analyzes results of obstaclesensing in accordance with positions of the proximity sensors 61 (620).Through analysis of the obstacle sensing results, it may be seen thatoutput signals from the proximity sensors 61 exhibit differentintensities in accordance with different sensing directions of theproximity sensors 61, as shown in FIG. 15. For example, when an obstacleis disposed in an extension direction of the auxiliary cleaning unit 21,output signals from the proximity sensors 61 exhibit higher intensitiesin the arrangement order of the proximity sensors 61 nearer to theauxiliary cleaning unit 21. In the illustrated case, it may be possibleto analyze the results of obstacle sensing, taking into considerationonly the output signal from the proximity sensor 61 disposed in theextension direction of the auxiliary cleaning unit 21. Also, it may bepossible to calculate the distance to the obstacle, based on an outputsignal from the proximity sensor 61 disposed at a sensor position B, Cor D.

The cleaning controller 241 analyzes whether the output signal from eachproximity sensor 61 is higher or lower than a predetermined criticalvalue. Here, the critical value corresponds to the distance from thebody 10 to the outermost portion of the auxiliary cleaning unit 21 inthe extension direction of the extension arm 107.

Subsequently, the cleaning controller 241 determines an extensionposition of the auxiliary cleaning unit 21, based on the results ofanalysis (630). The auxiliary cleaning unit 21 may extend to theextension position along an extension path 340 of the extension arm 107.The extension position of the auxiliary cleaning unit 21 corresponds toa position on the extension path 340 of the extension arm 107.

When the output signal from the proximity sensor 61 is higher than thepredetermined critical value, the cleaning controller 241 may determinethat, in association with the position of the proximity sensor 61, thereis an insufficient space to allow the auxiliary cleaning unit 21 toextend. In this case, from among the proximity sensors 61, each of whichoutputs a signal lower than the critical value, one proximity sensor 61outputting a signal having highest intensity is selected. Afterdetermining the position of the selected proximity sensor 61, thecleaning controller 241 determines an extension position of theauxiliary cleaning unit 21, based on the determined position of theproximity sensor 61. In the illustrated case, an extension position ofthe auxiliary cleaning unit 21 may be determined, based on an outputsignal from the proximity sensor 61 disposed at a sensor position B orD.

On the other hand, when the output signal from the proximity sensor 61is lower than the predetermined critical value, the cleaning controller241 may determine that, in association with the position of theproximity sensor 61, there is a sufficient space to allow the auxiliarycleaning unit 21 to extend. In this case, the cleaning controller 241determines the position of the proximity sensor 61, and then determinesan extension position of the auxiliary cleaning unit 21, based on thedetermined position of the proximity sensor 61. In this case, it may bepossible to extend the auxiliary cleaning unit 21 to a maximum extensionposition thereof.

Thereafter, the cleaning controller 241 adjusts an extension distance ofthe side arm 102, based on the determined extension position, to causethe auxiliary cleaning unit 21 to extend to the determined extensionposition (640).

Although adjustment of the extension distance of the auxiliary cleaningunit 21 upon controlling the auxiliary cleaning unit 21 has beendescribed as being carried out on the basis of the travel direction ofthe body 10, the adjustment may be carried out in the same manner as theabove-described cases, for an obstacle disposed in a direction otherthan the above-described directions of the body 10.

Also, although the above description has been given in conjunction with,for example, the right auxiliary cleaning unit 21, for convenience ofdescription, the same adjustment as described above may be carried outin conjunction with the left auxiliary cleaning unit 22.

Also, control of retraction of the auxiliary cleaning units 21 and 22may be carried out in a reverse manner to that of the above-describedcontrol of extension of the auxiliary cleaning units 21 and 22.

FIGS. 16 to 18 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure.

Referring to FIGS. 16 to 18, the cleaning controller 241 determines theshape of an obstacle, and controls extension or retraction of eachauxiliary cleaning unit 21 or 22, based on the determined shape of theobstacle.

When proximity sensors 61, which are provided in plural while beingdisposed around the body 10, output higher-intensity signals in thearrangement order of the proximity sensors 61 nearer to one lateral sideof the body 10, it may be determined that there is an obstacle in theform of a flat wall at the lateral side of the body 10. In this case,for the sensed obstacle, the cleaning controller 241 controls theauxiliary cleaning unit 21 or 22 such that the auxiliary cleaning unit21 or 22 is retracted after being maintained in an extended state for apredetermined time. Alternatively, the cleaning controller 241 maycontrol the auxiliary cleaning unit 21 or 22 such that the auxiliarycleaning unit 21 or 22 is extended after being maintained in a retractedstate for a predetermined time.

The cleaning controller 241 independently controls the left auxiliarycleaning unit 22 and the right auxiliary cleaning unit 21 such that theyare independently extended or retracted. In this case, when an obstacleis disposed only at the left or right of the body 10, the cleaningcontroller 241 performs a control operation such that only the left orright auxiliary cleaning unit 22 or 21 is extended or retracted.Alternatively, the cleaning controller 241 may perform a controloperation such that both auxiliary cleaning units 21 and 22 aresimultaneously extended or retracted.

On the other hand, even when there are three or more auxiliary cleaningunits, the cleaning controller 241 may control the auxiliary cleaningunits in the same manner as described above.

When output signals from a certain number of proximity sensors 61 havevalues gradually increasing from a predetermined value in thearrangement order of the proximity sensors 61 nearer to one lateral sideof the body 10, and output signals from a certain number of proximitysensors 61 have values gradually increasing from a predetermined valuein the arrangement order of the proximity sensors 61 nearer to the frontof the body 10, the cleaning controller 241 may determine that there areobstacles in the form of walls at the lateral side and front side of thebody 10, respectively, that is, there is an obstacle in the form of acorner wall. For the corner wall obstacle, the cleaning controller 241controls the auxiliary cleaning units 21 and 22 to be retracted afterbeing maintained in an extended state for a predetermined time. Also,the cleaning controller 241 controls the auxiliary cleaning units 21 and22 to be extended after being maintained in a retracted state for apredetermined time.

When an obstacle is disposed at the front side of the body 10, thecleaning controller 241 controls the auxiliary cleaning units 21 and 22to be simultaneously extended.

When the proximity sensors 61, output signals of which are higher than apredetermined value, do not output such higher signals in a continuousmanner, the cleaning controller 241 may determine that there is anobstacle having a smaller size than a reference size around the body 10.For such an obstacle having a smaller size than the reference size, thecleaning controller 241 controls the auxiliary cleaning units 21 and 22to be prevented from extending. The obstacle, which has a smaller sizethan a reference size, may be a flowerpot or a chair leg disposed on thefloor, on which the body 10 travels. When the auxiliary cleaning units21 and 22 extend in this case, they may strike the flowerpot, chair legor the like or they may interfere with obstacle-bypassing travel of thebody 10.

FIGS. 19 to 21 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure.

Referring to FIGS. 19 to 21, the cleaning controller 241 controlsextension or retraction of the auxiliary cleaning units 21 and 22 inaccordance with a travel direction of the body 10.

When the body 10 approaches an obstacle in the form of a corner wall,the cleaning controller 241 controls the auxiliary cleaning units 21 and22 to be simultaneously extended. In this case, the travel controller242 controls the drive wheels 41 and 42 such that the body 10 rotates inplace or moves backward, to bypass the obstacle.

In this case, the cleaning controller 241 may control the auxiliarycleaning units 21 and 22 to be retracted before the rotation or backwardmovement of the body 10. Also, the cleaning controller 241 may controlthe auxiliary cleaning units 21 and 22 such that a preceding one of theauxiliary cleaning units 21 and 22 in a rotation direction of the body10 is retracted before or after rotation of the body 10 in accordancewith the rotation direction of the body 10. Alternatively, the cleaningcontroller 241 may control the auxiliary cleaning units 21 and 22 suchthat a following one of the auxiliary cleaning units 21 and 22 in therotation direction of the body 10 is retracted before or after rotationof the body 10 in accordance with the rotation direction of the body 10.

Also, the cleaning controller 241 may control the auxiliary cleaningunits 21 and 22 such that the auxiliary cleaning units 21 and 22 extendby different distances in accordance with a rotation direction of thebody 10. For example, when the body 10 rotates in a counterclockwisedirection, the cleaning controller 241 may control the auxiliarycleaning units 21 and 22 such that the extension distance of the leftauxiliary cleaning unit 22 is reduced, and the extension distance of theright auxiliary cleaning unit 21 is increased.

Thus, when the body 10 travels while bypassing an obstacle in the formof a corner wall, it is possible to prevent the auxiliary cleaning units21 and 22 from striking the obstacle.

Even when there is a step on a bypass travel path of the body 10, thesame effect as in the above case may be obtained. In particular, evenwhen the step is not disposed on a travel path of the body 10, there maybe a possibility that the auxiliary cleaning units 21 and 22 strike thestep. In this case, accordingly, a preceding one of the auxiliarycleaning units 21 and 22 in a rotation direction of the body 10, forexample, the auxiliary cleaning unit 22, is controlled to be previouslyretracted. In this case, in order to allow the auxiliary cleaning unit21 following the auxiliary cleaning unit 22 in the rotation direction ofthe body 10 to be naturally retracted, electric power supplied to thearm motor of the auxiliary cleaning unit 21 may be reduced.Alternatively, spring structures may be employed for respectiveauxiliary cleaning units 21 and 22.

Meanwhile, when the body 10 performs bypass travel to bypass an obstaclein the form of a corner wall, the travel controller 242 may perform acontrol operation to reduce the travel speed of the body 10 whileincreasing the rotation speed of the auxiliary cleaning tool 110. Whenthe travel speed of the body 10 is reduced, the cleaning time for acorner wall is increased. When the rotation speed of the auxiliarycleaning tool 110 is increased, the number of times to sweep dust at acorner wall area is increased. Accordingly, there is an effect ofenhancing cleaning efficiency for a corner wall area.

FIGS. 22 to 24 are views schematically illustrating operation of therobot cleaner according to another embodiment of the present disclosure.

Referring to FIGS. 22 to 24, the cleaning controller 241 controlsextension or retraction of the auxiliary cleaning units 21 and 22 inaccordance with a cleaning mode of the body 10.

In an automatic cleaning mode, when an obstacle approaching the body 10is sensed, the cleaning controller 241 performs a control operation toextend the auxiliary cleaning units 21 and 22. When the robot cleaner 1starts a cleaning operation in accordance with the automatic cleaningmode, the cleaning controller 241 also performs a control operation toprevent the auxiliary cleaning units 21 and 22 from extending for apredetermined time.

In a return mode, the charging controller 243 performs a controloperation to return the body 10 to the charger 80. The cleaningcontroller 241 performs a control operation to prevent the auxiliarycleaning units 21 and 22 from extending while the body 10 returns to thecharger 80. Alternatively, the cleaning controller 241 may perform acontrol operation to prevent the auxiliary cleaning units 21 and 22 fromextending when it is determined that an obstacle sensed while the body10 returns to the charger 80 in the return mode is the charger 10.

When the robot cleaner 1 travels to return to the charger 80 aftercompleting cleaning, it is unnecessary to extend the auxiliary cleaningunits 21 and 22, for cleaning. When the auxiliary cleaning units 21 and22 are in an extended state, they may interfere with docking of the body10 with the charger 80.

Meanwhile, a signal transmitter 81 to transmit a discriminating signalis installed at the charger 80 in order to enable the cleaningcontroller 241 to discriminate the charger 80 from obstacles.

The discriminating signal may be an infrared signal 82 transmitted fromthe signal transmitter 81 to enable the robot cleaner 1 to trace theposition of the charger 80 or to dock with the charger 80, as shown inFIG. 22. In this case, the infrared signal 82 may be transmitted fromthe charger 80 in a radial manner or in a straight manner. When theinfrared signal 82 is transmitted from the charger 80 in a radialmanner, it may be divided into a low-power signal and a high-powersignal, to form two different signal zones. For example, the low-powersignal may form a signal zone enabling tracing of the position of thecharger 80, and the high-power signal may form a signal zone enablingdocking with the charger 80 during tracing of the position of thecharger 80.

The signal sensing unit 230 senses the infrared signal 82 transmittedfrom the charger 80. When the infrared signal 82 is sensed, the cleaningcontroller 241 determines that the charger 80 is disposed in front ofthe body 10, and then performs a control operation to prevent theauxiliary cleaning units 21 and 22 from extending until the body 10docks with the charger 80.

Alternatively, the discriminating signal may be a short-range radiofrequency (RF) signal transmitted from the charger 80. In this case, asshown in FIG. 23, an RF signal zone 83 is formed around the charger 80.When the body 10 enters the RF signal zone 83, the signal sensing unit230 may sense the short-range RF signal transmitted from the charger 80.Upon sensing the short-range RF signal, the cleaning controller 241determines that the charger 80 is disposed around the body 10, and thenperforms a control operation to prevent the auxiliary cleaning units 21and 22 from extending until the body 10 docks with the charger 80.

Also, the discriminating signal may be a magnetic field signal formedaround the charger 80. For example, when a magnetic belt 84 is installedat the charger 80 such that it surrounds a front surface, lateralsurfaces, overall surface or one surface of the charger 80, a magneticfield zone 85 may be formed around the charger 80 by the magnetic belt84. Of course, the magnetic belt 84 may have a shape other than a beltshape.

The signal sensing unit 230 senses the magnetic field formed around thecharger 80. When the magnetic field is sensed, the cleaning controller241 determined that the charger 80 is disposed around the body 10, andthen performs a control operation to prevent the auxiliary cleaningunits 21 and 22 from extending until the body 10 docks with the charger80.

The cleaning controller 241 also performs the control operation toprevent the auxiliary cleaning units 21 and 22 from extending in acharging mode, in which the body 10 performs a charging operation, in acharging completion mode, in which the charging operation of the body 10is completed, and the charging stop mode, in which supply of electricpower to the charger 80 is stopped during the charging operation of thebody 10.

The above-described operations of the robot cleaner 1 may be applied tothe exhaust station to exhaust dust collected in the robot cleaner 1 inthe same manner as applied to the charger 80.

Meanwhile, although the auxiliary cleaning units 21 and 22 of the robotcleaner 1 have been described as being coupled to left and light sidesof the body 10 in the above-described embodiments of the presentdisclosure, there is no limitation as to the number of auxiliarycleaning units and the installation positions of auxiliary cleaningunits.

As apparent from the above description, in accordance with one aspect ofthe present disclosure, it may be possible to adjust an extension orretraction degree of each auxiliary cleaning unit when an obstacle issensed. Accordingly, it may be possible to prevent the auxiliarycleaning unit from striking an obstacle, and to enhance cleaningefficiency for an area disposed adjacent to a wall, etc. In accordancewith another aspect of the present disclosure, it may be possible tocontrol extension or retraction of each auxiliary cleaning unit inaccordance with the shape of an obstacle. Accordingly, in this case, itmay be possible to reduce the cleaning time of the robot cleaner, and tofurther enhance cleaning efficiency for an area disposed adjacent to awall, etc. In accordance with another aspect of the present disclosure,it may be possible to control extension or retraction of each auxiliarycleaning unit in accordance with a travel direction of the body of therobot cleaner. In this case, accordingly, the robot cleaner may travelwithout striking an obstacle even when it performs obstacle-bypassingtravel. In accordance with another aspect of the present disclosure, itmay be possible to control extension or retraction of each auxiliarycleaning unit in accordance with a cleaning mode. Accordingly, in thiscase, the robot cleaner may rapidly return to the charger or exhauststation. Also, the robot cleaner may determine the charger or exhauststation as an obstacle, thereby preventing the auxiliary cleaning unitfrom striking the charger or exhaust station.

Although a few embodiments of the present disclosure have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the disclosure, the scope of which is definedin the claims and their equivalents.

What is claimed is:
 1. A robot cleaner comprising: a body to travel on afloor; an obstacle sensing unit to sense an obstacle approaching thebody; an auxiliary cleaning unit mounted to a bottom of the body, to beextendable and retractable; and a control unit to control extension orretraction of the auxiliary cleaning unit by adjusting an extension orretraction degree of the auxiliary cleaning unit when the obstacle issensed.
 2. The robot cleaner according to claim 1, wherein: theauxiliary cleaning unit is pivotably mounted to the bottom of the body;and the control unit adjusts the extension or retraction of theauxiliary cleaning unit, based on a pivot angle formed by the auxiliarycleaning unit with respect to a travel direction of the body.
 3. Therobot cleaner according to claim 2, wherein the control unit adjusts theextension or retraction degree of the auxiliary cleaning unit such thata distance between an outermost portion of the auxiliary cleaning unitand the obstacle is greater than a predetermined first critical value,but smaller than a predetermined second critical value.
 4. The robotcleaner according to claim 1, wherein the control unit compares anoutput signal from the obstacle sensing unit according to a sensingdirection of the obstacle sensing unit with a predetermined criticalvalue, and adjusts the extension or retraction degree of the auxiliarycleaning unit, based on a result of the comparison.
 5. The robot cleaneraccording to claim 4, wherein the predetermined critical valuecorresponds to a distance from the body to an outermost portion of theauxiliary cleaning unit.
 6. The robot cleaner according to claim 1,wherein the control unit adjusts the extension or retraction degree ofthe auxiliary cleaning unit, based on an output signal from the obstaclesensing unit according to an extension direction of the auxiliarycleaning unit.
 7. The robot cleaner according to claim 6, wherein thecontrol unit adjusts the extension or retraction degree of the auxiliarycleaning unit in proportion to the output signal.
 8. A robot cleanercomprising: a body to travel on a floor; an obstacle sensing unit tosense an obstacle approaching the body; at least one auxiliary cleaningunit mounted to a bottom of the body, to be extendable and retractable;and a control unit to control extension or retraction of the auxiliarycleaning unit in accordance with a shape of the sensed obstacle when theobstacle is sensed.
 9. The robot cleaner according to claim 8, whereinthe control unit controls the extension or retraction of the auxiliarycleaning unit when the obstacle has a flat wall shape such that theauxiliary cleaning unit is retracted after being maintained in anextended state for a predetermined time, or is extended after beingmaintained in a retracted state for a predetermined time.
 10. The robotcleaner according to claim 9, wherein: the at least one auxiliarycleaning unit comprises at least two auxiliary cleaning units mounted tothe bottom of the body; and when the obstacle is sensed only at alateral side of the body, the control unit only controls extension orretraction of the auxiliary cleaning unit, which is disposed in adirection corresponding to the obstacle, among the at least twoauxiliary cleaning units.
 11. The robot cleaner according to claim 8,wherein: the at least one auxiliary cleaning unit comprises at least twoauxiliary cleaning units mounted to the bottom of the body; and when theobstacle has a corner wall shape, the control unit controls extension orretraction of the auxiliary cleaning units, which are disposed atopposite sides of the body, among the at least two auxiliary cleaningunits.
 12. The robot cleaner according to claim 8, wherein the controlunit controls the extension or retraction of the auxiliary cleaning unitwhen the shape of the obstacle has a smaller size than a reference size.13. A robot cleaner comprising: a body to travel on a floor; an obstaclesensing unit to sense an obstacle approaching the body; at least oneauxiliary cleaning unit mounted to a bottom of the body, to beextendable and retractable; and a control unit to control extension orretraction of the auxiliary cleaning unit in accordance with a traveldirection of the body when the obstacle is sensed.
 14. The robot cleaneraccording to claim 13, wherein the control unit controls the auxiliarycleaning unit to be retracted before and after rotation of the body orbefore and after backward movement of the body.
 15. The robot cleaneraccording to claim 14, wherein: the at least one auxiliary cleaning unitcomprises at least two auxiliary cleaning units mounted to the bottom ofthe body around the body; and the control unit controls extension orretraction of the auxiliary cleaning units in accordance with a rotationdirection of the body such that a preceding one of the auxiliarycleaning units in the rotation direction of the body is retracted. 16.The robot cleaner according to claim 14, wherein the control unitcontrols extension degrees of the auxiliary cleaning units in accordancewith a rotation direction of the body such that a preceding one of theauxiliary cleaning units in a direction opposite to the rotationdirection of the body has an increased extension degree.
 17. The robotcleaner according to claim 14, wherein the control unit adjusts a travelspeed of the body or a rotation speed of an auxiliary cleaning toolcoupled to the auxiliary cleaning unit when the body rotates.
 18. Arobot cleaner comprising: a body to travel on a floor; an obstaclesensing unit to sense an obstacle approaching the body; an auxiliarycleaning unit mounted to a bottom of the body, to be extendable andretractable; and a control unit to control extension or retraction ofthe auxiliary cleaning unit in accordance with a cleaning mode of thebody when the obstacle is sensed.
 19. The robot cleaner according toclaim 18, wherein the control unit performs a control operation toprevent the auxiliary cleaning unit from extending when a cleaningoperation is completed.
 20. The robot cleaner according to claim 19,wherein the control unit performs a control operation to prevent theauxiliary cleaning unit from extending when the obstacle is determinedto be a charger or an exhaust station during return of the body to thecharger or the exhaust station.
 21. The robot cleaner according to claim20, further comprising: a signal sensing unit to sense a discriminatingsignal for the charger or the exhaust station.
 22. The robot cleaneraccording to claim 21, wherein the discriminating signal is an infraredsignal, a radio frequency (RF) signal, or a magnetic field signal. 23.The robot cleaner according to claim 18, wherein the control unitperforms a control operation to prevent the auxiliary cleaning unit fromextending for a predetermined time when a cleaning operation starts inaccordance with an automatic cleaning mode.
 24. The robot cleaneraccording to claim 18, wherein the control unit performs a controloperation to prevent the auxiliary cleaning unit from extending when thebody performs a charging operation.
 25. The robot cleaner according toclaim 24, wherein the control unit performs a control operation toprevent the auxiliary cleaning unit from extending when the chargingoperation of the body is completed or when supply of electric power tothe charger is stopped.
 26. A control method for a robot cleanercomprising: driving a body of the robot cleaner such that the bodytravels on a floor; sensing an obstacle approaching the body; andcontrolling extension or retraction of an auxiliary cleaning unitmounted to a bottom of the body, to be extendable and retractable, byadjusting an extension or retraction degree of the auxiliary cleaningunit.
 27. The control method according to claim 26, wherein: theauxiliary cleaning unit is pivotably mounted to the bottom of the body;and the controlling the extension or retraction of the auxiliarycleaning unit is executed, based on a pivot angle formed by theauxiliary cleaning unit with respect to a travel direction of the body.28. The control method according to claim 27, wherein the controllingthe extension or retraction of the auxiliary cleaning unit is executedsuch that a distance between an outermost portion of the auxiliarycleaning unit and the obstacle is greater than a predetermined firstcritical value, but smaller than a predetermined second critical value.29. The control method according to claim 26, wherein the controllingthe extension or retraction of the auxiliary cleaning unit is executed,based on a result of a comparison between an output signal from theobstacle sensing unit according to a sensing direction of the obstaclesensing unit and a predetermined critical value.
 30. The control methodaccording to claim 29, wherein the predetermined critical valuecorresponds to a distance from the body to an outermost portion of theauxiliary cleaning unit.
 31. The control method according to claim 26,wherein the controlling the extension or retraction of the auxiliarycleaning unit is executed, based on an output signal according to anobstacle sensing direction, along which the auxiliary cleaning unitextends.
 32. The control method according to claim 31, wherein thecontrolling the extension or retraction of the auxiliary cleaning unitis executed in proportion to the output signal.
 33. A robot cleanercomprising: a body to travel along a floor; a main brush unit; a powersupply, first and second drive wheels; a caster; at least one auxiliarycleaning unit, the auxiliary cleaning unit being extendable andretractable in a radial direction of the body, and comprising; a sidearm coupled to a front portion of a bottom of the body at one side ofthe body, the side arm being pivotable about a first coupling grooveformed at one end of the side arm; a second coupling groove formed at another end of the side arm; an auxiliary cleaning tool rotatably coupledto the second coupling groove; and a periphery cover attached to theother end of the side arm, the periphery cover forming an outer surfaceof the body when the auxiliary cleaning unit is in a fully retractedposition, an obstacle sensing unit to sense an obstacle approaching thebody; a control unit to control extension or retraction of the auxiliarycleaning unit, wherein the control unit adjusts the extension orretraction of the auxiliary cleaning unit based on a pivot angle of theside arm with respect to a travel direction of the body.
 34. The robotcleaner according to claim 33, wherein the control unit adjusts theextension or retraction degree of the auxiliary cleaning unit such thata distance between an outermost portion of the auxiliary cleaning unitand the obstacle is greater than a predetermined first critical value,but smaller than a predetermined second critical value.